This is the first in a series of articles for those of you who want to know a bit more about basic metal work, sometimes called fabrication. This is not complicated, no lost wax casting, bezel setting or soldering, just simple metal fabrication; but you can do a lot with simple techniques.
Besides, idols that had been objects of worship, even if for a day, were no more permitted to be taken out of Nepal since they were now a part of living culture.
Once a student gets over the excuses and learns how to put the blade in the saw frame, the next problem is finding an idea, something besides cutting out basic geometric shapes, which is where some people start.
Next, we pour molten wax into the mold. The layers of wax create an exact copy the original casting. Then, our craftspeople extract the wax from the mold and weld, polish, and add extra details. Then, we dip the fusione a cera persa into liquid clay multiple times and apply a layer of ceramic sand. Our artisans let the mold dry and then place it into a kiln.
The solution is then placed in a metal flask together with the wax mold. The solution will harden after a few hours together with the wax mold and will be placed in an oven to let the wax mold melt. This will leave a space on the investment which is where the melted gold or other metals is then poured and allowed to dry in order to take the shape of the mold.
The next step is gating. The fiberglass and rubber molds are gently removed from the wax mold, leaving an exact wax replica of the clay sculpture. Wax rods, called gates, are attached to the sculpture. These gates will create channels in the final mold, which allows for the molten bronze to be poured into the mold.
As for the silica sol investment steel casting workshops, they use the materials of yellow wax and silica solution. So, they can keep the higher level for the surface quality and dimensional requirements. According to the experience of Mr. Galen Wang from Dandong Ruiding Foundry, the silica sol investment casting process can reach the best surface quality and dimensions. Their problems are as same as the water glass investment casting process. They have size and weight restriction. In addition, their production costs are usually three times of water glass investment castings. Therefore, unless you need absolutely high surface quality and dimensions, this process is not your best choice.
Once the bronze has been poured and has cooled, the shell is then carefully chipped away, leaving a cast of the original sculpture in bronze. Any flaws are removed, the sculpture can be buffed and left its natural bronze color, or painted. This process is very labor intensive and expensive, but it results in such fine quality castings that it is still used after 4000 years.